What firewall ports does Qualys need opened to scan?
If you want to do an external scan to test what vulnerabilities an external person might see/exploit, then change your option profile in QualysGuard to scan all the ports that are open on your firewall.
If you want to do an internal scan to scan for vulnerabilities independent of the firewall, then simply place a scanner appliance inside your firewall and scan from there.
To see what ports Qualys scans by default, please see How does vulnerability scanning work?
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